PROJECT SUMMARY The filoviruses (family Filoviridae), comprising five ebolaviruses, a cuevavirus, and two Marburg viruses, are negative-strand RNA viruses that cause severe hemorrhagic fever with up to 90% human case fatality rate. The 2014?2016 epidemic in Western Africa, caused by the Zaire ebolavirus (EBOV) species demonstrated the potential for these viruses to cause dire health emergencies of global scope, and highlighted the need for development of therapeutics and vaccines. Sudan virus (SUDV), Bundibugyo virus (BDBV), and Marburg virus (MARV) have all caused large human outbreaks with high case fatality rates, and thus have similar epidemic potential. In particular, while SUDV, the subject of this proposal caused the 2nd largest filovirus outbreak to date, no therapy or vaccine is currently available. Our product, CM-SV1, is a humanized first-in-class, single dose, monoclonal antibody (mAb) against SUDV for use as both a prophylactic and a therapeutic agent, thus serving the needs of frontline medical staff and infected persons. mAbs represent an attractive therapeutic modality for filoviruses because mAb cocktails or convalescent IgG has been demonstrated to provide post-exposure protection of non-human primates. Furthermore, mAbs are generally well-tolerated and have favorable pharmacokinetic and safety profiles. Given the sporadic and unpredictable nature of outbreaks, it would be highly advantageous to have mAb therapies against each of the filoviruses ready for rapid deployment as emergency therapeutics. To date, we have produced CM-SV1 in both HEK293 and N. bethathasmia (tobacco) and have demonstrated efficacy in lethal challenge models in murine and guinea pig models of SUDV infection. The purpose of this proposal is to first determine developability of CM-SV1 and then to develop CM-SV1 to a technology readiness level (TRL) 5 in preparation for investigational new drug (IND) filing. In Phase I, we will engineer the Fc portion CM-SV1 to have improved prophylactic capabilities, produce CM-SV1 in an industry standard for manufacturing (Chinese Hamster ovary cells), determine developability, demonstrate non-inferior efficacy compared to HEK produced CM-SV1 in a murine challenge model, and determine success in engineering enhanced half-life. In Phase II, we will determine non-inferior efficacy compared to HEK produced CM-SV1 in a guinea pig challenge model, determine toxicity, prepare and file a pre-IND application and conduct a Type B meeting with FDA, and finally demonstrate efficacy of CM-SV1 in a non-human primate SUDV lethal challenge model. At the culmination of this program CM-SV1 will be optimized for cGMP manufacture and IND preparation.